According to the definitions of IUPAC, a macrocycle (MC) is a cyclic polymer generally containing more than 15 atoms (see IUPAC Compendium of Chemical Terminology 2nd Edition (1997)). The cyclic polymer or macrocycle has a variety of interesting physical properties, which are different from those of a common linear molecule and linear polymer (see J. Roovers, P. M. Toporowski, Macromolecules 1983; 16, 843; J. A. Semlyen, Cyclic polymers, 2nd ed. Dordrecht: Kluwer Publishers, 2000; and C. W. Bielawski, D. Benitez, R. H. Grubbs, Science 2002, 297, 2041), such as low viscosity, high solubility, and relatively low hydrodynamic volume. In recent years, in the development of polymer science and application, for example, discovering a polymer that has good compatibility with a solvent in a solution so as to lower the viscosity and increase the solubility has attracted considerable research interest. These occurrences mostly result from relatively less terminal functional groups in the structure of the cyclic polymer, leading to the distinctive properties that are different from those of a linear molecule and linear polymer. Presently, characteristic determinations of the cyclic polymer structure are primarily based on the low-hydrodynamic volume property of the cyclic polymer.
In the 1980s, many studies were involved with the syntheses of the cyclic oligomers and the applications thereof in the ring-opening polymerization. The study on the oligomeric cyclic carbonates of GE corporation, U.S., is the most celebrated case and shows great business potential (see J. C. Carnahan, U.S. Pat. No. 4,273,717 (1981); D. J. Brunelle, T. L. Evens, et al., Polymer Preprints 1989, 30, 569; E. P. Boden, D. J. Brunelle, et al., Polymer Preprints 1989, 30, 571; T. L. Evens, C. B. Berman, et al., Polymer Preprints 1989, 30, 573; K. R. Stewart, Polymer Preprints 1989, 30, 575). This process involves preparing a precursor, i.e., bisphenol A bischloroformate, from bisphenol A, followed by synthesizing oligomeric cyclic carbonates under pseudo-high dilution. The oligomeric cyclic carbonate is subject to ring-opening polymerization over an anionic catalyst, and converted into polycarbonate (PC) with a high molecular weight in an extruder at 250° C. for 2-5 minutes. Furthermore, due to the low viscosity of the oligomeric cyclic carbonates, the production capacity can be increased, and the difficulties in injection molding for a large object become solvable. This processing method with the macrocycle as a raw material in the reaction injection molding will be an important technology in the polymer industry.
However, it is necessary for the ring-opening polymerization of the oligomeric cyclic carbonates to be conducted under an elevated temperature above 250° C. to yield the product with high Tg and high molecular weight. Apparently, the polymer material prepared by the ring-opening polymerization of macrocycles has a disadvantage that the production mode has high energy consumption.
The syntheses of cyclic CDI involve two main species, which are aliphatic and aromatic cyclic CDI, respectively. R. Richter, et al. taught a process for synthesizing tridecacycloaliphatic CDI, which was a small ring cycloaliphatic CDI, by using 2-azacyclododecanone as an initiator (see R. Richter, B. Tuker, H. Ulrich, J. Org. Chem. 1981, 46, 5226; R. Richter, B. Tuker, H. Ulrich, J. Org. Chem. 1983, 48, 1894; and R. Richter, E. A. Barsa, J. Org. Chem. 1986, 51, 417). In addition, cycloaromatic CDI was not successfully synthesized until 1994 by P. Molina et al. (referring to P. Molina, M. Majarin, and P. Stinchez-Andrada, J. Org. Chem. 1994, 59, 7306; P. Molina, M. Majarin, and P. Stinchez-Andrada, J. Org. Chem. 1996, 61, 4289; and P. Molina, M. Majarin, and P. Stinchez-Andrada, et al., J. Org. Chem. 1998 63, 2922). However, for the method according to Molina, it was necessary to first prepare the costly intermediate, i.e., azophosphorane (N═P), and then perform the aza-Wittig reaction with a reagent, i.e., tBac2O/4-(dimethylamino)pyridine (DMAP), and the cyclization under high dilution to give a small ring cycloaromatic CDI.
In 1991, Nippon Painting Corporation, Japan, successfully synthesized linear diisocyanate by directly reacting six-membered ring cyclopropylene urea with bischloroformate to yield bis(cyclopropylene acylurea), and then performing ring-opening reaction of cyclopropylene acylurea by means of thermolysis, with the thermolysis property of N-acyl-N,N′-disubstituted urea to generate amide and isocyanate. Although cyclic acylurea has been successfully prepared, the initial raw material, i.e., cyclopropylene urea, is expensive, and merely a small ring cyclic (i.e., hexacyclo) acylurea could be obtained. This limits its applications.
Until now, an effective intermediate for synthesizing a cyclic polymer or macrocyclic intermediate has not been developed, and neither has an effective cyclic intermediate for synthesizing another cyclic functionalized polymer intermediates. Accordingly, the present invention is directed to a method for synthesizing macrocyclic CDI. Furthermore, MC-ACU can be produced by reacting the macrocyclic CDI with an organic acid in high selectivity, which may be further used as a novel MC-polymer intermediate for synthesizing an organic polymeric material, such as modified polyurethane (PU). In addition, the CDI functional groups in the macrocycle can react with carboxylic acid and water, and thus, the MC-CDI according to the present invention also can be added into a polymeric material as a dehydrating agent and an acid scavenger to further improve the durability of the polymeric material.